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DTM
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Raw image TCC
how weird that this image
does not include optically deep waters! | 
Raw image FCC
notice a strong atmospheric adjacency effect,
which mostly affects the Nir and Red bands |
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Adjacency effect
Blue and Green bands
seem to lack the adjacency effect......
Raw Blue band | Raw Green band |
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Adjacency effect
...which is very strong
in both Red and NIR bands
Raw Red band | 
Raw NIR band | |
Deglinted TCC
Ikonos images carry their own radiometric noise |  Deglinted Red band
threshold on the Red band must be set high enough |
spectral image LBS
a "low tide" true color composite of the scene | 
image B
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image Z
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Chequered LB image
has water column corrected bottom signature
or deglinted color composite
as BOA radiances, scaled 0-250 | 
Chequered LB image
has water column corrected bottom signature
or deglinted color composite
as BOA radiances, scaled 0-250 |
| | |
left insert: B right insert: Z
brighter sand waves are several meters shallower
than surrounding darker bottoms
| 
left insert: B right insert: Z
contrasted substrates drape
a gently sloping bottom
|
image LBS "normalized" - This image is intended as a contribution towards habitats mapping efforts by more established procedure
- Artifact areas (purple in the 3-bands case for BGRN images) are conspicuous to a seasoned practioner, and can be
- either corrected for by using the 2-bands case
- or flagged as turbid waters
| Local turbidity : the purple artifact
<== image LBS "normalized" - Two band case: areas in shades of grey do not exhibit significant bottom detection in the red band: ==>WZ=2
- Three bands case: areas with contrasted spectral bottom signatures exhibit significant bottom detection in the red band: ==>WZ=
- spectral contrast is enhanced by the "normalization" procedure for visual inspection
- Areas with greenish spectral bottom signatures are conspicuous
- this is where the optical calibration was assessed
- transition towards the two-bands case modeling is not noticeable in the computed depth image
- Increased water turbidity would apear to be the cause of purpleish spectral bottom signatures
- Locally more turbid waters
- decrease the bottom reflected signal mostly in the (nir and) red band, much less in the green and blue bands
- cause a shallower computed depth and a "dark/purpleish" darker spectral bottom signature
- cause an odd transition towards the two-bands case modeling in the computed depth image
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image WZ RED where 3-bands modeling was possible
GREEN where only Green/Blue modeling was possible In AbuDadi, the three-bands case
only applies to
a narrow ~800 m wide corridor
along the shoreline. | 
image WR
illustrates the diameter
of the circular smart-smoothing window
from 3 pixels to 5 pixels to... to 11 pixels
Smoothing takes care
of the noise in the signal |
